Distributed object systems are designed to increase the efficiency of computer program development by enabling object reuse and simplifying system maintenance through clear separation of functions. Each object in a distributed object system encapsulates the data for that object and the procedures or methods for operating on that data. Encapsulation means that the data for an object can be manipulated only by that object using the defined methods. These features of distributed object systems allow the objects to be reused and portable. Exemplary distributed object systems include: COM (Common Object Model), COM+, DCOM (Distributed Component Object Model) and CORBA (Common Object Request Broker Architecture).
One of the features of the distributed object system is a message service. A conventional message service system includes one or more publishers, subscribers and message servers. A publisher is a program (object or method) that makes calls that initiate sending messages that contain data, and a subscriber is another program (object or method) that receives the messages from a publisher. A subscriber indicates to (e.g., registers with) its message server that it wishes to receive messages from a publisher.
An exemplary conventional message service server is Message Queuing Services (MSMQ) developed by Microsoft may be used. MSMQ implements asynchronous message service by enabling applications (e.g., data providers) to send messages to other applications (e.g., data receivers). While the messages are being forwarded from senders to receivers, MSMQ keeps the messages in queues. The MSMQ queues may protect messages from being lost in transit and provide a place for receivers to look for messages when they are ready. MSMQ is configured to support IPX (Internet Packet exchange) and TCP/IP (Transmission Control Protocol/Internet Protocol) networking protocols. In the distributed object system parlance, a publisher is a data provider (e.g., the method sending the message) and a subscriber is a data receiver (e.g., the method receiving the message).
The conventional distributed systems fall short when messages are to be exchanged between a large number of publishers and subscribers, because in such a case the conventional message service system is required to predefine the relation between the data providers and data receivers (e.g., certain types of messages are predefined to be received by certain subscribers). In particular, the conventional system may provide adequate message services when all the relations are predefined and do not change. However, the conventional message system fails when the relations are to be dynamic. For example, assume a subset of the data providers are to send messages to one subset of the data receivers under one condition while the same subset of the data providers are required to send messages to another subset of the data receivers under another condition. Under such a scenario, the connections between data providers and data receivers are required to be updated dynamically (e.g., as the conditions change and/or as the messages are created).